1. Field of the Invention
This invention relates to vibration-damping constructions and a method useful for damping vibratory and/or noise emitting structures and component parts of devices such as automobiles, aircraft, industrial equipment, and appliances. This vibration-damping construction comprising at least a single layer of a thermoset resin. This invention further relates to a process of preparing the thermoset resins.
2. Description of Related Art
As technology moves toward energy conservation with the concomitant drive towards light weight structures that move at faster speeds and operate at higher temperatures, the acoustic and vibratory responses become larger and less desirable.
It has long been known that the vibration of component parts of devices and structures that vibrate under the influence of an applied internal or external force can be substantially reduced by the attachment of a layer of viscoelastic material. For example, U.S. Pat. No. 3,640,836 (Oberst et al.) describes a vibration-damping laminate in which the viscoelastic layer is a polymer comprised of ethylene, vinyl acetate and acrylic and/or methacrylic acid. U.S. Pat. No. 3,847,726 (Becker et al.) describes a viscoelastic adhesive composition of a polyepoxide, a polyether amine, a heterocyclic amine, and a phenol useful as vibration-damping material over a -25.degree. to +60.degree. C. range. Such compositions, however, are not effective for vibration-damping over prolonged periods of time at elevated temperatures.
U.S. Pat. No. 3,833,404 (Sperling et al.) describes viscoelastic damping compositions comprising an interpenetrating polymer network composition consisting essentially of 5-95% by weight of a polyalkyl acrylate elastomer, for example, polyethyl acrylate or polybutyl acrylate, polyvinyl acetate, polyurethane, polybutadiene, natural rubber, silicone rubber, butyl rubber, chloroprene, ethylene propylene terepolymer elastomers, polyvinyl alcohol, thiol rubber, and copolymers thereof; and 95-5% by weight of a plastic, such as polystyrene, poly-.alpha.-methyl styrene, polyalkyl acrylates, for example, polymethyl methacrylate or polyethyl methacrylate, poly-1-alkenes, for example, polypropylene, polyacrylic acid, and copolymers thereof, together with an outer plastic constraining layer.
Epoxies have traditionally been used as constraining layers in damping constructions since they do not exhibit any significant damping due to their highly crosslinked networks. Although U.S. Pat. No. 3,833,404 considers epoxy for the constraining layer, epoxy is not considered alone or in combination with other polymers as a potential viscoelastic damping material.
U.S. Pat. No. 4,385,139 (Kuchler et al.) describes a synthetic resin composition composed of at least two different polymers and a filler for use as starting material for vibration-damping sheets. In addition to at least one acrylic acid ester, at least one vinyl ester and inorganic filler, 1 to 10% by weight of an epoxide resin is added to the mixture relative to the sum total of the first 3 components.
U.S. Pat. No. 4,304,694 (Scala et al.) describes a damping composite comprising a resin matrix of about 20 to 43% by weight of a flexible epoxy, about 12 to 35% by weight of a stiff epoxy, about 35 to 61% by weight of a flexible crosslinking agent and about 20 to 50% by weight of a high modulus graphite fiber. The crosslinking agent described comprise a long chain amine-fatty acid amide.
U.S. Pat. No. 4,447,493 (Driscoll et al.) describes a constrained-layer damping construction containing a viscoelastic polymer that is the reaction product of (a) 25 to 75 weight percent of an acryloyl or methacryloyl derivative of at least one oligomer having a T.sub.g of less than 25.degree. C. and a molecular weight per oligomer of 600 to 20,000 and (b) 75 weight percent of a monomer whose homopolymer has a T.sub.g of at least 50.degree. C., the copolymer being suitable for damping vibrations at relatively high temperature, for example, 50.degree. to 150.degree. C. It appears that the 50.degree.-150.degree. C. damping regime was measured at a frequency of 1000 Hz. Since damping temperatures generally decrease about 6.degree. to 7.degree. C. with every decreasing decade of frequency, the copolymers described in the '493 patent would be expected to damp between about 30.degree. and 130.degree. C. at. 1 Hz.
U.S. Pat. No. 4,684,678 (Schultz et al.) describes epoxy resin compositions that on curing yield cured resins having a high glass transition temperature, high ductility, and low moisture pick-up. 9,9-bis(aminophenyl)fluorenes are used as the curing agents.
U.S. Pat. No. 4,707,534 (Schultz) describes diglycidyl ethers of ortho-substituted-4-hydroxy-phenylfluorenes curable compositions comprising diglycidyl ethers, and cured resins thereof. The cured resins have a high glass transition temperature and improved modulus of elasticity.
U.S. Pat. No. 4,216,288 (Crivello) describes heat curable cationically polymerizable organic materials, such as epoxy resins, based on using an aromatic onium salt, combined with a reducing agent.
U.S. Pat. No. 4,910,270 (Maekawa et al.) describes a curable epoxy resin composition comprising (a) an epoxy resin, (b) a glycol type di(meth)acrylate, (c) a nitrogen containing heterocyclic compound, and (d) a polyamine having at least two amino groups with an active hydrogen.
U.S. Pat. No. 5,008,324 (Killgoar et al.) describes a process of using compositions comprising certain thermoplastic elastomeric polymers for damping and damping compositions comprising soft thermoset polymer containing microscopically discrete segments of said thermoplastic elastomeric polymers.